Side elevation of the property

We’ve just replaced the boiler plant in a very large country residence in Sussex (July 2013).

The house sits in many acres of grounds

The old oil fired Worcester Bosch system heated the house, which was mainly comprised of 60 yr old radiators and large bore steel pipe, as an entire single entity without any zone control.  The oil bill (no mains gas here) was £12K per annum.

Our customer looked at a number of options, but liked our approach best.  Our unique proposal was to improve the efficiency of the boiler room by using weather compensation and load sharing – reduce consumption of oil and increase comfort, by zoning the house into to 16 areas.

Much of the radiator pipework was estimated to be in excess of 60 years old, and our Honeywell Hometronic wireless zone system was the ideal way to enable the house to be split up into 16 completely independent heating areas – without changing pipes or disfiguring the property with cabling.  Perfect for listed buildings!

Hometronic 16 zone controller

Each radiator (some probably 60yrs old) was fitted with a Honeywell HR80 control valve; these incorporate a motor, two temperature sensors, a digital display, and a manual override knob.   And two AA batteries (typical lifespan 3yrs).

The fitment of these units enabled us to have total control over the radiator heating, and divide the entire house into 16 areas chosen by our client.  Our customer could then decide which areas of the house would be warm, and which areas less warm, at specific times of the day!  As part of the installation, we programme different scenarios (eg: Christmas with guests, or 2 people and a housekeeper etc) as dictated by the owner,  and subsequently these can be simply selected at the push of a labelled button.


Honeywell HR80 being fitted to radiator

We featured the ability to control the heating, on a zone by zone basis, using a WebManager, which is a PC interface that links all the Hometronic features to an internet browser and the internet.   Furthermore, our customer is using an iPhone app by Crispbox solutions, which extends control over the heating system from anywhere in the World.

The app is called EnergyThift, (you can download a demo version from the Apple app store).  This is not a simple WiFi thermostat, but a 16 zone heating control, plus hot water management.   It only works with Hometronic.

Energythrift for iPhone

We removed the 155Kw boiler system comprising 2 30yr old Worcester boilers, and renewed all the plant around a modern Worcester-Bosch oil fired installation.  Bosch are giving us a 7yr warranty (Note: this post was made in July 2013) on their oil boilers, which was a comfort to the owners.

The boiler room was located in a basement, and the work entailed building a scaffolding frame and using a timber load ramp with a Tirfor cable hoist to haul the old 300kg units out, and lower the modern replacements in.

1981 Worcester 70Kw oil boilers

Boiler room was under water when we started

Hot Water was provided by an ACV SL420 ‘tank in tank’ cylinder.  This 300Kg unit was winched into the boiler house down the same ramp we’d constructed for the boilers.  The ACV unit works very well with oil boilers, because the heat transfer from the boiler to the stored water allows up to 65Kw of energy to be transferred, reducing boiler cycling on/off to an absolute minimum.  It does this by using a corrugated stainless steel hot water tank submerged inside a steel tank full of boiler water.

Scaffolding rig to enable safe removal of the old boilers by winch

Plywood ramp made for getting the old plant out, and the new equipment in. Of course we resisted the temptation to use it as a slide into the boiler room. Any mats lying around?

The 35 yr old Worcester boilers are being replaced by a pair of new Worcester-Bosch Greenstar Utility50-70 oil fired condensing units.  The boilers are linked to a custom built distribution low loss header system of our own design.

300Kg Worcester unit coming out

One of the new Worcester Bosch 50/70 Greenstar units on the way down. These weigh 300Kg too, which is why Ricky is taking a picture from the side rather than from the base…. Water is added to the plywood to reduce friction.

New plant positioned and ready to be connected up. The 7ft high ACV cylinder was also 300Kg. Seems everything on this job is big, and heavy.

A ‘Honeywell Smile’ building management unit is used to manage the boiler room.

The Honeywell Smile controller determines the boiler use;  in summer months it will cycle the two boilers individually to maximise economy and spread the running time equally across the units.  In the colder winter months it will bring on both boilers simultaneously as and when external temperatures demand a high heating load, typically when the Hometronic 16 zone system is in a ‘guests at home’ lifestyle (in other words, when the house is fully occupied and all radiators are on).

Honeywell Smile boiler room controller

The Honeywell Smile is self contained and does not need to operated or configured in any way once installed.

The boiler house flue system has been upgraded, with the existing chimney being relined and a common flue header system being run across the boiler plant room, using condensing flue technology.

New condensing flue header, linking two Worcester Bosch boilers

The house is on three floors, and problems hadbeen experienced with the 2nd floor radiators not fully filling and venting.  This was because the radiator header tank was actually lower than the tops of the radiators.  Resiting the header tank on the roof of the property would probably have voided the listed status, but also caused other problems with freezing in cold weather.

Our solution was to convert the radiator system from a conventional feed and expansion tank, to a sealed system.  We have installed a Mikrofill AFD automatic fill system, which is a patented system with no pumps, using mains water pressure.  The Mikrofill monitors the water pressure in the system, and makes adjustments automatically.  (Most combination boilers and more recent boiler installations in the UK use a manual ‘filling loop’ or tap to top up the heating system, for commercial sized systems this is not practical, so the Mikrofill carries out the process without human intervention).

Mikrofill Automatic Filling Device

Radiator system expansion vessels (2×300 litres) linked to Mikrofill filling device


Each boiler has a dedicated Grundfos system pump

The power and lighting was upgraded as part of our work

New boiler system


ACV tank in tank cylinder completed


The low loss distribution header where the boiler outputs are mixed


Grundfos Magna2 varispeed pump for central heating, with weather compensation mixing valve behind

On an old system like this, where there is over 1500 litres of water in large bore pipework and a mixture of iron, steel and copper radiators, it is inevitable that there will be a significant amount of debris in the water.  Powerflushing, commonly used on domestic systems, is not workable at these pipe sizes, so we fitted a very high specification commercial sized magnetic dirt filter by SpiroTECH.  This unit, recently launched in the Netherlands, was specially imported to the UK for this project.

It works by having a removable spring loaded magnet of large proportions fitted inside a chamber, which attracts ferrous particles. At the same time, the SpiroTECH patented series of gauzes separates and drops non-ferrous material into a sump.

We found this filter to be very effective, and in the first few months of operation it will be emptied weekly to help cleanse the system of contamination.  Each time the SpiroTECH is purged (into a bucket) the Mikrofill AFD (auto filling device) recharges the system with water.

Commercial sized Magnetic and Non Ferrous dirt filter on 3″ pipework


Close up of the commercial SpiroTECH MAGNET dirt separator unit

The highest quality components were used throughout, including Belimo actuators, Grundfos pumps, Honeywell controls and Worcester-Bosch boilers.  Although the building was Grade 2 listed, the internal and external aspects remain unchanged, just the boiler room has been changed.  Even the flue system used the original chimney stack.

This large upgrade, designed and installed by Hot Water & Central Heating Ltd  in consultation with the owners, was completed in July 2013.